With distance, some weapons will experience a reduction in damage called 'drop off'.
Drop off by weaponEditMost ranged weapons are distance penalized with drop off. Generally a weapon will do maximum damage from point blank, up until some other distance (D1). From there, the weapon will start to lose damage at a steady rate until it reaches a second point (D2). From D2 further out the weapon generally will not lose any additional effect up until the maximum range of the gun.
Head shots Experience the same percentage of drop off, as do any other hit location. Thus a normal shot that loses 15% damage at 150meters will expect the head shot damage to also come down 15%.
Both Plasma Pistol and Plasma Cannon in either firing mode have no drop of due to distance. Oddly, the standard fire mode of the Plasma Gun *does* experience drop off.
The Vengence Launcher does not have any drop off for its direct hit damage.
Explosions have drop off relative to the epicenter of the blast.
The Melta Gun has a drop off more like an explosion, with multiple distance points and modifiers.